OTRS (Open Technology – Real Service) is an open source ticket request system with many features to manage customer telephone calls and emails. It is distributed under the GNU General Public License (GPL) and tested on various Linux platforms.  OTRS

Update CentOS 7.x to specific version.

How to update CentOS 7.x to specific version or upgrading the Centos 7.x System Off-line with ISO and Yum.
In this tutorial we will show you, how to configure and use local yum repository and upgrade Centos 7.x to a specific version. For example 7.2 to 7.4

1) On Centos 7.2 server run the following Commands.
# yum install net-tools
# yum install wget
# yum install vsftpd
# systemctl start vsftpd.service
# systemctl enable vsftpd
# yum install createrepo

2) Disable SELinux
# vi /etc/selinux/config
Change: SELINUX=disabled
Save the file
# cat /etc/system-release
# reboot

3) Download Centos 7.4 and mount the .iso file.
# cd /root
# mkdir Software
# cd Software
# wget http://mirror.nsc.liu.se/centos-store/7.4.1708/isos/x86_64/CentOS-7-x86_64-Minimal-1708.iso
# cd /media
# mkdir ISO
# mount -o loop /root/Software/CentOS-7-x86_64-Minimal-1708.iso /media/ISO

4) Copy Centos 7.4 media content to the Server.
# mkdir /localrepo
# cp -rv /media/ISO/* /localrepo/

5) Configure a Local Repository.
First we need to backup current repository folder.
# cd /etc
# cp -r yum.repos.d yum.repos.d-old

Now delete all online repository and create local Repository File.
# rm -rf yum.repos.d/*
# vi yum.repos.d/local.repo

Add the following:
[centos74]
name=centos74
baseurl=file:///localrepo/
enabled=1
gpgcheck=0

Save the file and exit.

[centos74] – Name of the Section.
name = Name of the repository
baseurl = Location of the package
Enabled = Enable repository
gpgcheck= Enable secure installation

gpgcheck is optional (If you set gpgcheck=0, there is no need to mention gpgkey)
gpgkey = Location of the key

6) Now we need to update, and enable  the local repository.
# createrepo /localrepo/
# yum clean all
# yum repolist all

7) Update Centos 7.2 to 7.4 ussing local repos.
# yum update